Sacrificial anode assembly

ABSTRACT

A method of using and a steel reinforced concrete protector in an anode cavity which comprises a cored hole, a drilled hole or a cut chase formed in concrete. The protector comprises a sacrificial anode assembly and a separate backfill. The sacrificial anode assembly comprises a sacrificial metal element that is a metal less noble than steel and an activator to maintain an activity of the sacrificial metal element. The at least one spacer prevents the sacrificial metal element and the activator from contacting the surface of the anode cavity. The spacer and the sacrificial metal element have a coupling mechanism which facilitates connection of the sacrificial metal element to the spacer. The backfill is a pliable and viscous material which contains an electrolyte, and the backfill facilitates embedding the anode assembly in the anode cavity. The invention also relates to a prepackaged sacrificial anode assembly and a method of increasing a shelf life of the sacrificial anode.

This application is a Continuation of U.S. patent application Ser. No.13/290,496 filed Nov. 7, 2011, which claims priority from British patentapplication serial no. 1018830.8 filed Nov. 8, 2010.

FIELD OF THE INVENTION

This invention concerns the protection of steel in concrete using one ormore sacrificial anode assemblies where the one or more sacrificialanode assemblies are embedded within cavities formed in the concreteand, more specifically, where the cavities are mechanically formed forthe purposes of accommodating the one or more sacrificial anodeassemblies.

BACKGROUND OF THE INVENTION

Reinforced concrete structures sometimes suffer deterioration becausethe reinforcing steel eventually corrodes. This is often caused bychloride contamination or carbonation of the concrete. Sacrificialanodes are used to inhibit the corrosion of steel in concrete.Sacrificial anode assemblies, embedded within cavities formed inconcrete, typically comprise a sacrificial metal that is less noble thansteel (i.e., electrochemically more negative than steel) such as zinc,an activator for maintaining an activity of the sacrificial metalelement, a backfill for accommodating the products of the sacrificialmetal dissolution and a ductile elongate metal conductor forinterconnecting the sacrificial metal element with the steel or to apower supply.

In some cases-typically the case when a consumed activator is used, thebackfill and the activator will be assembled with the sacrificial metaland the conductor in a factory and this assembly will then be installedon site by embedding the assembly in a cementitious mortar in a cavityformed within the concrete. In cavities formed as the result ofcorrosion damage, the sacrificial anode assembly will be “tied” orotherwise electrically coupled or connected to the steel beforesubstantially filling the cavity with a concrete repair material inorder to restore the exterior profile and properties of the concretesubstantially back to its original state. In other cases, an anodecavity (for example, a drilled hole) may be mechanically formed for thepurpose of installing a sacrificial anode assembly and, in this case,the anode cavity will be substantially filled with the assembly (seeRepair Application Procedure 8 published by the American ConcreteInstitute at www.concrete.org/generall/RAP-8.pdf).

More recent developments include assembling the components of asacrificial anode assembly within an anode cavity. For example, asacrificial metal element may be embedded directly in a backfill locatedin the anode cavity, as disclosed in U.S. Pat. No. 8,002,964. The anodecavity may also open into a larger cavity formed as the result ofcorrosion damage to protect the steel in the adjacent undamagedconcrete.

It is to be appreciated that the embedded sacrificial anodes, forreinforced concrete structures, need to be activated if they are toprovide the desired protection to the reinforcing steel. Activators forsacrificial anodes may be described as a consumed activator or acatalytic activator. An example of an activator that is consumed ishydroxyl ions. The hydroxyl ions react with the sacrificial metalelement to produce a soluble species. It is to be appreciated that withthis form of activation, the functional life of the sacrificial anodeassembly depends on the quantity of the activator present. Suchactivators are generally pre-assembled as an anode-backfill assembly. Itis to be appreciated that such activators may also be aggressive to theparent concrete by, for example, causing an adverse alkali silicareaction to occur within the parent concrete.

Examples of catalytic activators—which include halide ions and sulphateions—are found in, for example, U.S. Pat. No. 7,749,362. The halide ionsrender passive films on a sacrificial metal element unstable. Oneproblem associated with this form of activation is that such activatorsalso tend to be aggressive with respect to the reinforcing steel andthis can cause corrosion problems.

Another problem with sacrificial anode assemblies containing activatorsis that they may, when located in contact with the air, graduallydeteriorate because an active metal in contact with an activatornormally suffers from atmospheric corrosion. As a result, this phenomenatends to limit the shelf life of such a sacrificial anode assembly.

Sacrificial anode assemblies are sometimes used in combination with apower supply to deliver an impressed current treatment, for example, asdisclosed in U.S. Pat. No. 7,909,982. This arrangement can be also usedto draw chloride ions, present in the concrete, to the sacrificial metalelement to activate the anode assembly. In this case, an activator(s)may not be required and an increased shelf life of the assembly can beachieved.

When a sacrificial anode assembly is assembled from components andplaced within a cavity formed in an underside or a downwardly facingopening in a reinforced concrete element another problem occurs, namely,the anode may fall out of the cavity due to the effect of gravity untilsuch time as the backfill sufficiently hardens or a concrete repairmaterial covers the assembly to prevent inadvertent removal thereof.

SUMMARY OF THE INVENTION

Wherefore, it is an object of the present invention to overcome theabove mentioned shortcomings and drawbacks associated with the prior artassemblies and techniques.

An objective of the present invention is to provide a method of using acatalytic activating agent or a catalytic activator in a manner thatdoes not place the reinforcing steel at risk of having substantialcontact with the catalytic agent or activator once sacrificial anodeassembly or assemblies are assembled in the anode cavities which areformed within concrete.

Another objective of the present invention is to retain the anode, theactivator and the backfill in place following assembly within a cavityformed in the underside or downwardly facing surface of a reinforcedconcrete element.

A further objective of the present invention is to provide a method ofincreasing the shelf life of the sacrificial anode assembly, containingan activator, that would normally deteriorate once the sacrificial metalelement and the activator are exposed to air and/or moisture.

A still further objective of the present invention is to provide amethod of protecting steel, when located in concrete, using asacrificial metal element which comprises a metal less noble than steel,an activator, a backfill and at least one spacer, the method comprisingthe steps of:

forming an anode cavity in the concrete for the purposes of installing asacrificial anode assembly therein,

locating the sacrificial metal element and the activator within thebackfill contained within the cavity, the backfill being selected suchthat the backfill remains pliable and viscous and does not harden untilafter the installation process is completed,

using the spacer to space the sacrificial metal element and thecatalytic agent or activator away from the surfaces of the cavity, and

supplying a current from the sacrificial metal element to the steel inthe concrete to protect the steel in the concrete.

In one preferred embodiment the spacer is a housing spacer with a borein which the sacrificial metal element is housed. In another embodiment,the spacer is a plurality of resilient plastic wedges or other elementsthat hold or retain the sacrificial metal element spaced away from theinwardly facing surface or sides of the anode cavity. The plastic wedgesmay be secured to the sacrificial metal element by one or more rubberbands, cable ties, or other conventional fasteners. The plastic wedgesneed not be secured to the sacrificial metal element and may only belocated within the cavity once the sacrificial metal element is placedwithin the cavity.

The spacer is preferably a resilient member. The resilient property maybe achieved by forming the spacer from either a metal or a plastic. Thespacer may be a resilient plastic spacer. Examples of a plastic that maybe used include acetyl and polypropylene. If a metal spacer is utilized,preferably the metal spacer is insulated or covered and this may beachieved by coating at least the exterior surface of the metal spacerwith a conventional polymer. The spacer preferably substantiallycomprises a polymer which imparts resilience or insulates the resilientcomponent.

The spacer preferably includes at least one aperture or bore into whichthe sacrificial metal element may be received, accommodated or otherwisehoused. The spacer preferably grips, couples and captively retains thesacrificial metal element to the spacer. During use, the spacerpreferably holds and maintains the sacrificial metal element in a spacedarrangement with respect to the inwardly facing surface of the cavity.The spacer preferably holds and spaces the sacrificial metal element andthe catalytic agent or the activator away from the inwardly facingsurface of the anode cavity. This may be achieved by sizing the anodecavity in the concrete and the spacer such that the spacer grips thesacrificial metal element and exerts a sufficient pressure against theinwardly facing surface of the anode cavity once the spacer is locatedin the cavity. In this example, the spacer is placed under compressionin the anode cavity and the pressure between the spacer and the inwardlyfacing surface of the cavity results in the spacer sufficiently grippingthe inwardly facing surface of the cavity so as to captively retain thesacrificial anode assembly within the cavity.

The anode cavity is a three dimensional space. The spacer(s) preferablylocates the sacrificial metal element and the catalytic agent or theactivator generally at the center of at least one dimension of the anodecavity. The spacer(s) may also locate the sacrificial metal element andthe catalytic agent or the activator at the center of two dimensions ofthe anode cavity, e.g., both radially as well as axially along thelength of the drilled or cored hole.

The sacrificial metal element and the activator are preferably assembledtogether with one another prior to being embedded within the anodecavity. The activator may be applied as a coating to the sacrificialmetal element. Such a coating will typically comprise a binder and theactivator. A catalytic activator may be applied as a relatively thincoating. One example of the binder is calcium sulphate which also actsas the catalytic agent or activator. Another example of the binder is anoutdoor metal paint that may be thinned with an organic solvent. In thiscase, the binder is inert and the quantity of an inert binder ispreferably maintained below 20% of the dry coating weight. Thickercoatings may be applied using hydraulic cement, as a binder, to containa consumed activating agent. The spacer is also preferably assembledwith the sacrificial metal element and the activator prior to embeddingthe assembly within the anode cavity.

In one preferred embodiment, the activator is a catalytic activator.Examples of suitable catalytic agents/activators are disclosed, forexample, in U.S. Pat. No. 7,749,362 and U.S. Pat. No. 7,731,875. Thequantity of the catalytic agent or activator included with thesacrificial metal element should preferably be sufficiently small suchthat assuming that the catalytic agent or the activator is uniformlydistributed throughout the anode cavity, the catalytic agent or theactivator will be diluted to a concentration that is insufficient topresent any substantial corrosion risk to the steel to be protectedwithin the concrete. Thus corrosion risk presented to the steel by thecatalytic agent or the activator, once the sacrificial metal element hasbeen totally consumed, will be negligible.

In another embodiment, the activator is a consumed activator. Examplesof a consumed activator are potassium hydroxide or sodium hydroxide. Toavoid a deleterious alkali silica reaction between such an activator andthe parent concrete, it is preferable to keep the activator away fromthe parent concrete while the activator is consumed by reactions at theanode.

It is to be appreciated that combinations of both consumed and catalyticactivators are also envisaged and included as part of the presentinvention.

Examples of suitable backfills, for use with the present invention, aredisclosed in U.S. Pat. No. 8,002,964. The backfill may also be a powdermixed with water to produce a paste when installing the sacrificialanode assembly, an example of which would be a weak air entrained cementmortar paste. The backfill is preferably placed within the anode cavityand the sacrificial anode assembly, comprising an assembled metalelement, the catalytic agent or the activator and a spacer arepreferably pressed into the backfill previously located within the anodecavity. The backfill preferably retains its viscous and pliableproperties for at least 48 hours and more preferably the backfillretains these properties for a longer period of time (e.g., at least oneweek and more preferably at least one month) as this feature renders thebackfill practical for storage within a container, such as a cartridge,for an extended period of time. One example of such a preferablebackfill is a lime mortar paste.

The anode cavity is preferably a cored or drilled hole or a cut chasewhich is normally mechanically formed within the concrete in aconventional manner. The sacrificial metal element preferably consistsof zinc or a zinc alloy. A conductor is attached to the sacrificialmetal element to facilitate the flow of the galvanic electrical currentfrom the sacrificial metal element to the steel to be protected. Theconductor is preferably integrally assembled with the sacrificial metalelement to form an integrated unit which is separate from the concrete.The conductor may comprise a steel or a titanium wire. The sacrificialmetal element is preferably cast around at least a leading end portionof the conductor. The conductor may be attached directly to the steel todeliver a galvanic current, or may be first connected to the steel, viaa power supply, to deliver an impressed current which may precede thesubsequent galvanic current. When the conductor is to be connecteddirectly to the steel, the conductor preferably is an elongate ductileconductor having a length of at least 250 mm or greater to facilitateease of connection and avoid the need to splice conductors to completethe connection.

In another aspect this invention provides a steel reinforced concreteprotector for use in a cored hole, a drilled hole or a cut chase inconcrete comprising an anode assembly and a separate backfill whereinthe sacrificial anode assembly comprises a sacrificial metal element andan agent or an activator and a spacer for locating the sacrificial metalelement and the agent or the activator in a spaced relationship awayfrom the inwardly facing surface of the cored hole, the drilled hole orthe cut chase, and the sacrificial metal element comprises a metal lessnoble than steel and the backfill is a viscous and pliable backfill forembedding the sacrificial anode assembly in the hole.

In another aspect this invention provides a method of extending theshelf life of a sacrificial anode assembly comprising a sacrificialmetal element less noble than steel and an activating agent oractivator, wherein the sacrificial metal element and the activatingagent or the activator are assembled together with one another andstored within a plastic bag or some other suitable container in which atleast water vapor, oxygen and/or carbon dioxide are removed from the airstoring the sacrificial anode assembly.

In one arrangement, the air is sucked out of or otherwise removed fromthe bag or the other container, under vacuum, and then the opening tothe bag or the other container is sealed in a conventional manner. Thepreferred process for packaging and sealing is conventionally known asvacuum packing and used in the food processing industry. In the case ofa bag, the bag will have at least one face that is dimpled to facilitatethe flow of air out of the bag and, once the required vacuum for theinterior cavity of the bag is achieved, the opening of the bag is thensealed by a conventional heating and melting process which seals theopposed surfaces of the bag, defining the opening, together.

The spacer and the elongate connector may be assembled with thesacrificial metal element and a catalytic agent or the activator, orassembled therewith prior to installation. It is to be appreciated thatthe plastic, forming the plastic bag, must be sufficiently thick androbust so as to avoid being punctured during the vacuum packing processas well as during shipment and handling thereof. If desired ornecessary, it is to be appreciated that more than one layer of plasticmay be used to resist the bag from being inadvertently punctured.

In the place of vacuum packing the anode-activator assembly orsacrificial anode assemblies, the sacrificial anode assembly may besealed, along with an inert gas or other fluid, within the interiorcavity of the plastic bag or other container. For example, oxygen,carbon dioxide and/or water vapor may be removed from the gas containedwithin the interior cavity or the storage compartment of the plastic bagin order to prevent deterioration and preserve the life of thesacrificial anode assembly to be stored within the bag or othercontainer. Alternatively, an inert gas or other fluid may be added tothe interior cavity or storage compartment of the plastic bag, alongwith the sacrificial anode assembly, to facilitate storage and resistdeterioration of the sacrificial anode assembly.

A method of protecting steel in concrete using one or more sacrificialanode assemblies comprising a sacrificial metal element, an agent or anactivator, a pliable viscous backfill and a conductor, may involveexposing the steel, at an area requiring concrete patch repair, formingan anode cavity comprising a cored or a drilled hole in the concreteadjacent to an area of patch repair for purposes of installing thesacrificial anode assembly therein, embedding the sacrificial metalelement and the agent or the activator in the backfill within the anodecavity and spacing the anode and the activator away from the inwardlyfacing surface or sides of the anode cavity via at least one spacer,connecting the sacrificial metal element to the exposed steel located inthe adjacent patch repair, via an elongate ductile conductor having asufficient length to extend from the sacrificial metal element to thesteel without the need for splicing, wherein the elongate ductileconductor is assembled with the sacrificial metal element prior toembedding the sacrificial metal element. The agent or the activator ispreferably a catalytic agent or a catalytic activator and the spacer ispreferably assembled with the catalytic agent or the activator andsacrificial metal element to create a space that is filled with thebackfill between the activator and the inwardly facing surface or wallsof the cored or drilled hole. The catalytic agent or the activator andthe spacer are preferably preassembled with the sacrificial metalelement prior to installation.

The present invention also relates to a steel reinforced concreteprotector, for use in an anode cavity, comprising: a cored hole ordrilled hole or cut chase in concrete comprising a sacrificial anodeassembly and a separate backfill wherein the sacrificial anode assemblycomprises a sacrificial metal element that is a metal less noble thansteel; an activator to maintain an activity of the sacrificial metalelement; at least one spacer that prevents the sacrificial metal elementand the activator from contacting a surface of an anode cavity; thespacer and the sacrificial metal element have a coupling mechanism whichfacilitates retention of the sacrificial metal element to the spacer;and the backfill is a pliable and viscous material which contains anelectrolyte, and the backfill facilitates embedding the anode assemblyin the anode cavity.

The present invention also relates to a prepackaged sacrificial anodeassembly comprising: a sacrificial metal element comprising of a metalless noble than steel and including an activating agent being at leastone of coated on a surface of the sacrificial metal element andintegrally mixed with the sacrificial metal element; an elongateconnector being connected to the sacrificial metal element; at least onespacer for preventing contact between the sacrificial metal element anda surface of an anode cavity, and a coupling mechanism for coupling thesacrificial metal element to the spacer; and the sacrificial anodeassembly, following manufacture thereof, being sealed within a packagewhich is substantially free of at least one of oxygen, water vapor andcarbon dioxide.

The present invention also relates to a method of protecting steel inconcrete using a sacrificial metal element, an activator, a backfill andat least one spacer, the method comprising the steps of: forming ananode cavity in the concrete, and the anode cavity being sized so as tobe substantially filled by the sacrificial metal element, the activatorand the backfill; placing the sacrificial metal element, the activatorand the backfill in the anode cavity; using at least one spacer to spacethe sacrificial metal element and the activator away from an inwardlyfacing surface of the anode cavity; and passing a current from thesacrificial metal element to the steel; wherein the sacrificial metalelement comprises a metal less noble than steel, and the backfill issufficiently pliable and viscous so that the backfill does not hardenuntil after an installation process of the sacrificial metal element,the activator and the backfill is completed.

The present invention also relates to a method for increasing a shelflife of a sacrificial anode assembly comprising the steps of: assemblingof the sacrificial metal element less noble than steel with an activatorto maintain an activity of the sacrificial metal element and form thesacrificial anode assembly; and sealing the sacrificial anode assemblywithin a package which is substantially free of at least one of oxygen,water vapor and carbon dioxide to increase a shelf life of thesacrificial anode assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with referenceto the accompanying drawings in which:

FIG. 1 is a diagrammatic cross sectional view of the sacrificial anodeassembly, according to the present invention, contained within a sealedcontainer, and FIG. 1A is a similar diagrammatic cross sectional viewdiagrammatically showing the activator intimately mixed with anddispersed within and throughout the sacrificial metal element;

FIG. 2 is an isometric side view of the spacer of FIG. 1;

FIG. 3 is a top plan view of the spacer described of FIG. 1;

FIG. 4 is a diagrammatic sectional view showing the sacrificial anodeassembly of FIG. 1 being inserted and captively retained within anoverhead cavity;

FIG. 5 is a diagrammatic sectional view showing two, sequentiallyarranged spacers for supporting a longer or elongate sacrificial metalelement within a cavity;

FIG. 6 is a diagrammatic sectional view showing the sacrificial anodeassembly of FIG. 5 inserted and captively retained within a cavity;

FIG. 7 is a diagrammatic sectional view showing a longer alternativearrangement of the spacer for supporting a longer sacrificial metalelement within a cavity;

FIG. 8 is a diagrammatic sectional view showing an alternativearrangement for the retaining members for supporting the sacrificialmetal element within a cavity; and

FIG. 9 is a diagrammatic cross sectional view of a repaired steelreinforced concrete element which illustrates use of the sacrificialanode assembly according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning first to FIGS. 1 to 3, a description concerning the variouscomponents of the present invention will now be briefly discussed. Ascan be seen in this embodiment, FIG. 1 shows a sacrificial anodeassembly 2 which comprises a generally cylindrical sacrificial metalelement 4 which has an elongate ductile connector 6 extending from atrailing first end thereof. The sacrificial metal element 4 includes acatalytic activating agent or a catalytic activator 8 (onlydiagrammatically shown) and both the sacrificial metal element 4 and thecatalytic activating agent or the catalytic activator 8 are at leastpartially received and accommodated within a central bore 10 of agenerally cylindrical spacer 12. Following completion of assembly of thesacrificial anode assembly 2, the sacrificial anode assembly 2 is sealedwithin a substantially evacuated container 14 (only diagrammaticallyshown), as generally shown in FIG. 1, which is substantially free ofoxygen, water vapor and/or carbon dioxide so as to inhibit the catalyticactivating agent or the catalytic activator 8 from reacting with thesacrificial metal element 4 and thereby improve the storage or shelflife of the sacrificial anode assembly 2.

The housing spacer 12 comprises a generally elongate cylindrical body 16which has both a leading end 18 and a trailing end 20 and the centralbore 10 facilitates insertion of the sacrificial metal element 4 in thehousing spacer 12. When the sacrificial anode assembly 2 is insertedinto a cavity 22 provided with an electrolytic backfill 24, as discussedbelow in further detail and generally shown in FIG. 4, the backfill 24provides communication between the sacrificial metal element 4 and theadjacent concrete 26. The housing spacer 12 is designed to surround andat least partially encase and enclose the sacrificial metal element 4and prevent both the leading end surface as well as the perimeter sidesurface of the sacrificial metal element 4 from directly contacting withthe concrete 26, i.e., as generally shown in FIG. 1, the leading endsurface of the sacrificial metal element 4 is spaced axially inwardlyand away from the leading end 18 of the housing spacer 12 so as to avoidcontact with the concrete 26.

The exterior surface of the housing spacer 12 has a plurality ofradially outwardly extending retaining members 28 which facilitatespacing and generally centering of the housing spacer 12, and thuscentering of the sacrificial anode assembly 2, radially with respect tothe walls or inwardly facing surface 30 of the cavity 22 (see FIG. 4) aswell as retention of the sacrificial anode assembly 2 within the cavity22. The interior surface 40 of the housing spacer 12 has one or morenub(s), protrusion(s) or annular member(s) 32 located for engagementwith the at least one annular groove or recess 34 formed in thesacrificial metal element 4 for coupling, connecting and captivelyretaining the sacrificial metal element 4 to the housing spacer 12.

As noted above, the sacrificial metal element 4 has at least one annulargroove or recess 34 formed within the exterior surface of thesacrificial metal element 4. The at least one annular groove or recess34 is located so as to engage with the one or more nub(s), protrusion(s)or annular member(s) 32, supported by interior surface 40 of the housingspacer 12, and maintain a secure engagement between the sacrificialmetal element 4 and the housing spacer 12. Generally there is sufficientplay between the at least one annular groove or recess 34 and the one ormore nub(s), protrusion(s) or annular member(s) 32 so as to permit somerelative movement therebetween while still securely coupling thesacrificial metal element 4 to the housing spacer 12. It is to beappreciated that a variety of other types of conventional couplingmechanisms or arrangements, for reliably coupling or connecting thesacrificial metal element 4 to the housing spacer 12, may be utilizedinstead of the at least one annular groove or recess 34 and the one ormore nub(s), protrusion(s) or annular member(s) 32, as discussed above,without departing from the spirit and scope of the present invention.

One challenge with off site or pre-application or integration of anactivating agent or an activator with the sacrificial metal element 4 isthat the activating agent or the activator typically begins reactingwith the sacrificial metal element 4 as soon as the activating agent orthe activator is applied to or mixed with the sacrificial metal element4 in the presence of oxygen and water vapor. Furthermore, it is to beappreciated that carbon dioxide may also react with the sacrificialmetal element to form a metal carbonate passivating layer on thesacrificial metal element. In order to minimize such reaction(s), it isnecessary to package the coated sacrificial metal element 4, or thesacrificial metal element 4 with the integral activating agent or theactivator, generally within an environment which is free of reactivegasses or within a container 14 shortly after combining the sacrificialmetal element 4 with the catalytic activating agent or the activator,e.g., typically within 14 days after assembling or combining thosecomponents with one another.

A preferred method of gas free packaging of the sacrificial anodeassembly 2 is a conventional vacuum packaging process in which thesacrificial anode assembly 4 is vacuum sealed within an evacuatedplastic bag or container 14, and this process is discussed below infurther detail. Other methods of inert packaging of the sacrificialanode assembly 2 are envisioned and contemplated, such as packaging thesacrificial anode assembly 2 in a quantity of a non-reactive gas(es),such as nitrogen, or argon, which is sealed within the sealed container14 along with the sacrificial anode assembly 2. Examples of suitablecontainers 14 for packaging the sacrificial anode assembly 2 includesealed plastic bags, both hard or soft plastic containers, metalcontainers, shrink wrap packaging, etc.

The housing spacer 12 is preferably a material that is designed forcentering and maintaining the sacrificial metal element 4 in a spacedrelationship within the cavity 22. The housing spacer 12 must besufficiently stiff such that it will not collapse under the weight ofthe sacrificial metal element 4. As described above, the housing spacer12 is preferably assembled with the sacrificial metal element 4 and thecatalytic activating agent or the catalytic activator 8, prior toembedding or placing the sacrificial anode assembly 2 within the cavity22, but such assembly could be performed on site if desired ornecessary.

The housing spacer 12 preferably is cylindrically shaped and a diameterof the central bore 10 of the housing spacer 12 is larger than adiameter of an exterior surface 36 of the sacrificial metal element 4.It is to be appreciated that the housing spacer 12 can also be conicalor venturi shaped and/or have a varying distance between the interiorsurface 40 of the housing spacer 12 and the exterior surface 36 of thesacrificial metal element 4. The housing spacer 12 ideally has acylindrical body 16, so as to substantially match the preferablycylindrical shape of the sacrificial metal element 4, but the housingspacer 12 may also have a cross section that is triangular, rectangular,pentagonal, hexagonal, or some other desired shape.

For sacrificial metal element 4 having a length of less than about 75mm, typically only one housing spacer 12 is used, while for sacrificialmetal elements 4 having a length greater than 75 mm, typically thesacrificial metal element 4 accommodates two or more sequentiallyarranged housing spacers 12 (see FIGS. 5 and 6). When two or moresequentially arranged housing spacers 12 are utilized for the longersacrificial metal elements 4′, it is to be appreciated that such longersacrificial metal elements 4′ are provided with two or more sequentiallyarranged and spaced apart annular grooves or recesses 34, each locatedfor receiving and accommodating the one or more respective nub(s),protrusion(s) or annular member(s) 32 of the respective housing spacer12.

The body 16 of the housing spacer 12 is typically solid, but the body 16may include one or more interruptions 38 such as holes, slots, windows,perforations or apertures (only shown in dashed lines in FIG. 2) inorder to increase ion flow and conductivity through the body 16 of thehousing spacer 12. While such interruptions 38 in the body 16 of thehousing spacer 12 will generally increase the conductivity, they alsowill simultaneously reduce the structural integrity of the housingspacer 12, and increase the possibility the sacrificial metal element 4may inadvertently directly contact the reinforcing steel 35. In view ofthis drawback, the number, the size, the spacing and the location of theinterruptions 38 in the body 16 should be designed so as to avoid thesacrificial metal element 4 from contacting the reinforcing steel 35.

FIGS. 1 and 4 shows the plurality of nub(s), protrusion(s) or annularmember(s) 32, supported by the interior surface 40 of the body 16 of thehousing spacer 12, received within the annular groove or recess 34 ofthe sacrificial metal element 4 so as to facilitate a reliable but arelatively loose interconnection therebetween. Since the radial inwardlylength of the plurality of nub(s), protrusion(s) or annular member(s) 32is greater than the radial depth of the annular groove or recess 34 ofthe sacrificial metal element 4, an annular gap 42 is formed between theexterior surface 36 of the sacrificial metal element 4 and the interiorsurface 40 of the body 16 of the housing spacer 12. This gap 42 permitsthe electrolytic backfill 24 to directly contact and electrochemicallycouple and connect the sacrificial metal element 4 with the concrete 26.

The size of the gap 42, located between the interior surface 40 of thehousing spacer 12 and the exterior surface of the sacrificial metalelement 4, is preferably sufficient so that the gap 42 to be at leastpartially filled with a small quantity of the conductive electrolyticbackfill 24. By providing a gap 42 between the housing spacer 12 and thesacrificial metal element 4 and using a conductive electrolytic backfill24, which is sufficiently pliable to penetrate into the gap 42 betweenthe housing spacer 12 and the sacrificial metal element 4, the otherwisenegative effect of the housing spacer 12, on the current output of thesacrificial anode assembly 2, becomes negligible. This effect isdependent on the conductivity and fineness of the backfill and thepresence of the activating agent. The effect of the housing spacer 12 oncurrent output is not significant when the gap 42 is about 1 mm and limeputty is used as a backfill 24. The housing spacer 12 also has nosignificant effect on the current output when the gap is completelyfilled with activating agent.

Preferably, there are between two and eight nub(s), protrusion(s) orannular member(s) 32. The nub(s), protrusion(s) or annular member(s) 32may ideally have a wedge shaped profile, as generally shown in FIG. 1.This permits the sacrificial metal element 4 to easily be slid andsnapped in place within the internal bore 10 of the spacer 12, and becaptively retained therein once the one or more nub(s), protrusion(s) orannular member(s) 32 are received within and engage with the at leastone annular groove or recess 34. The nub(s), protrusion(s) or annularmember(s) 32 can be coplanar, axially spiral, or axially randomlydistributed. It is to be appreciated that the size, the number and thelocation of nub(s), protrusion(s) or annular member(s) 32 are selectedso as not to compromise the open area through which ions can flow intoand out of the housing spacer 12. In an alternative embodiment, thenub(s), protrusion(s) or annular member(s) 32 could each be coupled toor formed as an annular ring which is sized to engage with the annulargroove or recess 34 formed in the sacrificial metal element 4.

It is to be appreciated that in the place of, or in addition to,protrusions 32 located on the interior surface 40 of the housing spacer12, separate protrusions may be formed on exterior of the sacrificialmetal element 4 that would engage a mating groove(s), hole(s),recess(es) or indentation(s) formed in the interior surface 40 of thehousing spacer 12.

The plurality of retaining members 28 of the housing spacer 12 typicallyextend both axially and radially from at least adjacent one trailing end20 of the housing spacer 12, as generally shown in FIGS. 1-4. Theretaining members 28 each have a sufficient length so as to engage withan inwardly facing surface 30 of the cavity 22 and thereby assist withboth retaining and maintaining the housing spacer 12, and thus thesacrificial metal element 4, centered in place, even in an overheaddownwardly facing cavity 22, as well as assists with retaining thebackfill 24 within the cavity 22. The size, the number and the spacingof the retaining members 28 are generally limited to maximize the openarea through which ions can flow past the retaining members 28. Forexample, the housing spacer may have between three and ten retainingmembers 28 integrally formed with the housing spacer 12. Each retainingmember 28 preferably has a width of between 2 and 8 mm, and a length ofbetween 7 and 25 mm. The angle at which the retaining members 28 projectaway from the exterior wall of the housing spacer 12 assists withapplying a desired “spring” or retaining pressure, e.g., a compressionforce, by which the retaining members 28 engage with the inwardly facingsurface 30 of the cavity 22 and thereby retain the sacrificial anodeassembly 2 and the backfill 24 in their installed position.

The angle formed between the retaining members 28 and the housing spacer12 is preferably between about 30 degrees and 70 degrees. As eachretaining member 28 generally tapers radially away from the housingspacer 12, from the leading end of the sacrificial anode assembly 2toward the trailing end of the sacrificial anode assembly 2. Such taperfacilitates ease of insertion of the sacrificial anode assembly 2 withinthe cavity 22, as the retaining members 28 are each easily deflectedradially inward somewhat as the outer ends or edges of the retainingmembers 28 engage with and slide along the inwardly facing surface 30 ofthe cavity 22. Once the sacrificial anode assembly 2 is completelyreceived within the cavity 22, so that the leading end 18 abuts againsta base of the cavity 22 as generally shown in FIG. 4, the outer ends oredges of the retaining members 28 have a tendency, due to the angle thatthey project from the exterior surface of the housing spacer 12, to becompressed by and thus frictionally engage against the inwardly facingsurface 30 of the cavity 22 and thereby facilitate a secure retention ofthe sacrificial anode assembly 2 within the cavity 22.

During a typical installation, the sacrificial anode assembly 2 isinserted into a cavity 22, which is typically a cored or a drilled holeor a cut chase, mechanically formed in the concrete 26 containing thesteel to be protected and located adjacent to exposed steel 35 that isconnected to the steel to be protected. The cavity 22 is typicallycylindrical in shape and has a diameter of between 15 and 100 mm, e.g.,typically approximately between 25 and 50 mm, and a depth of between 35and 500 mm, typically approximately between 35 and 300 mm, which issized to receive one or more desired sacrificial anode assemblies 2. Itis to be appreciated that the diameter cavity 22 must be larger thanexterior surface of the housing spacer 12, but is preferably smallerthan the outer diameter D (see FIG. 3) of the retaining members 28 sothat the retaining members 28 can engage with and be deflected somewhatby the inwardly facing surface 30 of the cavity 22, as the desiredsacrificial anode assembly 2 is received therein, and frictionallyretain the sacrificial anode assembly 2 within the cavity 22, even in anoverhead cavity 22. Typically, the cavity 22 will have a length which issomewhat longer than a total axial length of the sacrificial anodeassembly 2.

The preferred process for packaging the anode assembly 2 is vacuumpacking, a process used in the food processing industry. In this case,the vacuum bags will preferably have at least one face that is dimpledto facilitate the flow of air out of the bag and, once the requiredvacuum is achieved, the opening of the bag is sealed by conventionallyheating and melting of the overlapped plastic layers together. Theplastic forming the plastic bag should be sufficiently thick and durableso as not be easily punctured during the vacuum packing process. Morethan one layer of plastic may be used to avoid the bag from beinginadvertently punctured during the packaging, shipping, distribution orsales processes. The vacuum packaging greatly increases the shelf lifeof the sacrificial anode assembly 2.

As noted above, a suitable backfill 24, to be used with the anodeassembly is disclosed in U.S. Pat. No. 8,002,964, and such disclosure isfully incorporated herein, as see GB 2430 938. The backfill 24 isideally a pliable, putty-like, ionically conductive material. Thebackfill 24 is typically preferably first placed within the cavity 22and then the complete sacrificial anode assembly 2 is preferably presseddirectly into the backfill 24, accommodated within the cavity 22, whichmay cause some of the backfill 24 to be displaced from inside the cavity22. It is to be appreciated that this process may, for someapplications, be reversed. The backfill 24 is selected such that thebackfill 24 retains its plasticity during the installation.

In order to install the sacrificial anode assembly 2, as noted above,the cavity 22 is first cored or drilled into the concrete 26. Then asufficient quantity of the pliable, electrolytic backfill 24 is placedwithin the cavity 22. Next, the sealed, evacuated container 14,containing the preassembled sacrificial anode assembly 2, is opened andthe sacrificial anode assembly 2 is then inserted into the backfill 24located within the cavity 22, the leading end 18 of the housing spacer12 first, so that the connector 6 remains located outside of the cavity22. If a preassembled sacrificial anode assembly 2 is not available,then the sacrificial anode assembly 2 should preferably be assembled onsite for insertion as a sacrificial anode assembly into the cavity 22.Lastly, the connector 6 is then connected to a desired piece of thesteel 35, and located within the concrete 26, in a conventional manner.

Turning now to FIG. 5, this Figure shows two sequentially arrangedhousing spacers 12 which both accommodate a portion of the longerelongate sacrificial metal element 4. The two housing spacers 12 bothassist with maintaining the longer elongate sacrificial metal element 4spaced radially from the inwardly facing surface 30 of the cavity 22during use, as shown in FIG. 6. Due to the sequential arrangement of thehousing spacers 12 as well as the manner in which the housing spacers 12each accommodate a portion of the longer elongate sacrificial metalelement 4′, the backfill 24 is still readily able to flow in and aroundthe longer elongate sacrificial metal element 4′, during operation ofthe sacrificial anode assembly 2.

Turning now to FIG. 7, this figure shows an elongate housing spacer 12′which accommodates a substantial portion of the longer elongatesacrificial metal element 4′. According to this embodiment, the elongatehousing spacer 12′ is provided with two sets of spaced apart retainingmembers 28 which both assist with maintaining the elongate housingspacer 12′ generally centered within the cavity 22 and thereby space thelonger elongate sacrificial metal element 4′ from the inwardly facingsurface 30 of the cavity 22 during use, as generally shown in FIG. 7. Inorder to facilitate passage of the backfill 24 around the sacrificialmetal element 4, during operation of the sacrificial anode assembly 2,as well as the flow of ions, one or more openings interruptions 38 maybe provided within the body 16 of the elongate housing spacer 12′.

Turning now to FIG. 8, an alternative arrangement of the retainingmembers 28 of the housing spacer 12 is shown. According to thisembodiment, the retaining members 28 each generally have an oval shapewhich extends from adjacent the leading end 18 toward the trailing end20 of the housing spacer 12, e.g., forms a taper profile. Such taperedprofile facilitates ease of insertion of the sacrificial anode assembly2 within the cavity 22 since the intermediate sections 28 of theretaining members 28 are easily deflected radially inward somewhat asthose sections of the retaining members 28 engage with and slide alongthe inwardly facing surface 30 of the cavity 22. Once the sacrificialanode assembly 2 is completely received within the cavity 22, so thatthe leading end 18 abuts against a base of the cavity 22, theintermediate sections 28′ of the retaining members 28 are compressed byand thus frictionally engage against the inwardly facing surface 30 ofthe cavity 22 and thereby facilitate a secure retention of thesacrificial anode assembly 2 within the cavity 22.

It is to be appreciated that a variety of other types of other retainingmembers 28, e.g., wedges, etc., may be utilized for generally centeringand retaining the housing spacer 12 and/or the sacrificial metal element4 and the catalytic activating agent or the catalytic activator 8,within the cavity 22, without departing from the spirit and scope of thepresent invention. The important feature of the retaining members 28 isthat they must generally frictionally engage with the inwardly facingsurface 40 of the cavity 22 so as to generally center and retain atleast the sacrificial metal element 4 within the cavity 22.

With reference now to FIG. 9, this Figure shows the sacrificial metalelement 4 and the housing spacer 12 embedded in a backfill 24 locatedwithin an anode cavity 22 that may be, for example, a 25 mm diameter by40 mm deep hole which is mechanically drilled or otherwise bored orformed within a concrete 26. The sacrificial metal element 4 may becoated with a catalytic activating agent or catalytic activator. Theanode cavity 22 opens into an adjacent cavity 44 that was formed becauseof corrosive damage. In this adjacent cavity 44, a steel bar 35 wasexposed and cleaned, in a conventional manner. The elongate ductileconnector 6 interconnects the sacrificial metal element 4 with the steelbar 35 in order to deliver a galvanic protection current from thesacrificial metal element 4 to reinforcing steel (not shown) locatedwithin the concrete 26 that is connected to the steel bar 35, duringuse.

As described above, a first end of the elongate ductile connector 6 isformed or embedded within or otherwise connected with the sacrificialmetal element 4 while the second opposite end of the elongate conductor6 is sufficiently long so as to facilitate a secure electrical clampingor connection with the steel bar 35, for example, via a conventionalcable tie 46 which makes and maintains the electrical connectiontherebetween in a secure and substantially permanent manner. Steel orstainless steel tie wire may also be used to secure the connection. Oncethe sacrificial anode assembly 2 is installed, as generally describedabove and shown in FIG. 9, then the adjacent cavity 44 is filled with anappropriate concrete repair material 48 so that both the sacrificialanode assembly 2 and the steel bar 35 are embedded within andsubstantially covered by the concrete repair material 48. During suchrepair, a cavity 22 is drilled typically at 500 mm intervals in theconcrete 26 around the periphery of the cavity 44 and a respectivesacrificial anode assembly 2 is located within each one of thosecavities 22 and connected, as described above, so as to provide thedesired galvanic current protection.

The sacrificial metal element 4 is a metal less noble that steel, andpreferably comprises either zinc or a zinc alloy. The sacrificial metalelement 4 is preferably cast as a cylindrical shaped body, but it is tobe appreciated that the sacrificial metal element 4 may be shaped into avariety of other shapes or configurations, such as regular polygonprisms. The sacrificial metal element 4 generally has a constant crosssection along its length, but the cross-sectional shape of thesacrificial metal element 4 may vary depending upon the particularapplication. The sacrificial metal element 4, which is designed to fitwithin a 28 mm diameter by 50 mm long cavity 22, will typically have adiameter or width of 18 mm and a length of 40 mm.

The elongate ductile connector 6 facilitates convenient connection ofthe sacrificial metal element 4 to the steel without the need to spliceany additional conductor directly to the sacrificial metal element 4during the installation process. The connector 6 may be a steel or atitanium wire. The connector 6 typically has a length of between 250 and400 mm and a diameter of between 0.7 and 2 mm. The connector 6 ispreferably at least partially embedded within the trailing end of thesacrificial metal element 4 and may extend the entire length of thesacrificial metal element 4. More preferably, the sacrificial metalelement 4 is cast around at least a portion of connector 6 with theconnector 6 extending out from the trailing end of the sacrificial metalelement 4 for a sufficient distance to facilitate ease of connection ofthe remote free end of the connector 6 with the steel 35 reinforcementin the concrete 26 to be protected.

As noted above, the sacrificial metal element 4 is assembled with thecatalytic activating agent or catalytic activator 8. That is, either theexterior surface 36 of the sacrificial metal element 4 is coated withthe catalytic activating agent or the catalytic activator 8, e.g., acompound(s) containing halide ions and sulphate ions, or alternatively,as diagrammatically shown in FIG. 1A, the catalytic activating agent orcatalytic activator 8 is intimately mixed with and dispersed within andthroughout the sacrificial metal element 4.

The quantity of the catalytic activating agent or catalytic activator 8,to be included with the sacrificial metal element 4 should preferably besufficient to provide the desired ion flow between the sacrificial metalelement 4 and the concrete 26 but insufficient to create a significantcorrosion risk by the catalytic activating agent or catalytic activator8 to the steel 35 once the sacrificial metal element 4 has beenconsumed. Preferably the quantity of catalytic activating agent orcatalytic activator 8 is such that if it were to be uniformlydistributed within the cavity 22, the catalytic activating agent orcatalytic activator 8 would be diluted to a concentration that isinsufficient to present a corrosion risk to steel embedded within theconcrete 26. For a chloride activator, this equates to a quantity ofless than 1.6 kg of chloride ions per cubic meter of anode cavity.

As indicated above, the catalytic activating agent or catalyticactivator 8 can be coated on the exterior surface 36 of the sacrificialmetal element 4 or integrated into and throughout the sacrificial metalelement 4, or both, and that the same the catalytic activating agent orthe catalytic activator 8 or two different the catalytic activatingagent or the catalytic activator 8 may be applied to the sacrificialmetal element 4. Ideally the catalytic activating agent or the catalyticactivator 8 is applied to or integrated into the sacrificial metalelement 4, prior to packaging the sacrificial anode assembly 2 forshipment and subsequent sale or installation. This allows theinstallation process of the sacrificial anode assembly 2 within a cavity22, at the installation site, to proceed at a faster rate than if thecatalytic activating agent or the catalytic activator 8 was manuallyapplied to each sacrificial metal element 4, on site, prior toinstallation or was injected into a porous anode body afterinstallation.

Since certain changes may be made in the above described sacrificialanode assembly, without departing from the spirit and scope of theinvention herein involved, it is intended that all of the subject matterof the above description or shown in the accompanying drawings shall beinterpreted merely as examples illustrating the inventive concept hereinand shall not be construed as limiting the invention.

1-25. (canceled)
 26. A method of protecting steel in concrete using a sacrificial metal element, an activator, a backfill and at least one spacer, the method comprising the steps of: forming an anode cavity in the concrete, and the anode cavity being sized so as to be substantially filled by the sacrificial metal element, the activator and the backfill; placing the sacrificial metal element, the activator and the backfill in the anode cavity; using at least one spacer to space the sacrificial metal element and the activator away from an inwardly facing surface of the anode cavity; and passing a current from the sacrificial metal element to the steel; wherein the sacrificial metal element comprises a metal less noble than steel, and the backfill is sufficiently pliable and viscous so that the backfill does not harden until after an installation process of the sacrificial metal element, the activator and the backfill is completed.
 27. The method according to claim 26, further comprising the step of using the at least one spacer for captively retaining the sacrificial metal element and the activator within the anode cavity in a spaced relationship from an inwardly facing surface of the anode cavity, and the at least one spacer being retained by compression of at least one retaining member extending radially outwardly from the at least spacer, the at least one retaining member engaging with the inwardly facing surface of the anode cavity once the assembly is inserted within the anode cavity.
 28. The method according to claim 26, further comprising the step of assembling the sacrificial metal element with the activator prior to locating the sacrificial metal element and the activator in the anode cavity.
 29. The method according to claim 28, further comprising the step of, following assembly of the sacrificial metal element and the activator, sealing the sacrificial metal element and the activator within a package which is substantially free of at least one of oxygen, water vapor and carbon dioxide, in order to increase a shelf life of the sacrificial anode assembly.
 30. The method according to claim 26, further comprising the step of coupling the sacrificial metal element to the at least one spacer via a coupling mechanism.
 31. The method according to claim 26, further comprising the step of housing the sacrificial metal element within an internal bore formed in the at least one spacer.
 32. The method according to claim 26, further comprising the step of connecting the sacrificial metal element to the steel, via a conductor, and passing a current from the sacrificial metal element to the steel.
 33. The method according to claim 26, further comprising the step of using a catalytic activator as the activator, and selecting the sacrificial metal element from the group consisting of at least one of zinc and a zinc alloy.
 34. A method of increasing a shelf life of a sacrificial anode assembly, the method comprising the steps of: assembling of the sacrificial metal element less noble than steel with an activator to maintain an activity of the sacrificial metal element and form the sacrificial anode assembly; and sealing the sacrificial anode assembly within a package which is substantially free of at least one of oxygen, water vapor and carbon dioxide in order to increase a shelf life of the sacrificial anode assembly.
 35. The method according to claim 34, further comprising the step of, prior to sealing the sacrificial anode assembly within a package, removing substantially all oxygen from an interior compartment of the package accommodating the sacrificial anode assembly.
 36. The method according to claim 34, further comprising the step of, prior to sealing the sacrificial anode assembly within a package, removing substantially all water vapor from an interior compartment of the package accommodating the sacrificial anode assembly. 